System and method for reducing shadow effects in touch systems

1. A method of reducing shadow effects in a touch system, the method comprising:

receiving a touch input on a touch interface from a finger or a stylus, wherein receiving a touch input comprises receiving touch signals from a plurality of sensor nodes of the touch interface, the touch signals including information from each of the plurality of sensor nodes representing an x position value, a y position value, and an amplitude of the touch input;

determining an arithmetic mean of the touch input, the arithmetic mean indicating a first estimated touch position of the touch input on the touch surface;

determining a weighted mean of the touch input, wherein the weighted mean is determined in part by applying a higher weight to the touch signals having a higher amplitude, the weighted mean indicating a second estimated touch position of the touch input on the touch interface;

determining a difference between the weighted mean of the touch input and the arithmetic mean of the touch input; and

adjusting the second estimated touch position of the touch input to a final estimated touch position based on the difference.

2. The method of claim 1 , wherein adjusting the second estimated touch position comprises adjusting one or more of the x position value, the y position value, and the amplitude of the second estimated touch position to the final estimated touch position based on the difference between the weighted mean of the touch input and the arithmetic mean of the touch input.

3. The method of claim 2 , wherein adjusting the second estimated touch position to the final estimated touch position comprises adjusting the second estimated touch position to the value of a centroid when the difference is below a first threshold and to a value based on the difference when the difference is equal to or above the first threshold.

4. The method of claim 1 , further comprising

identifying a maximum amplitude of the touch input of the received touch signals.

5. The method of claim 1 , wherein the touch interface is divided into a plurality of sectors by sector divisions to determine which sectors of the touch interface contain shadow effects of the touch input.

6. The method of claim 5 , wherein the sector divisions pass through one of a sensor node located closest to the weighted mean of the touch input or the arithmetic mean of the touch input.

7. The method of claim 5 , wherein the touch interface is divided into sectors by sector divisions that pass through a sensor node of the touch interface having a maximum touch signal strength as compared to the touch signal strengths of all of the sensor nodes in the touch input.

8. The method of claim 5 , further comprising:

sorting the touch signals in a descending order list such that the touch signal with the highest value occurs first in the list;

determining a maximum value of the touch signals and adding the maximum value to an extracted touch signal;

sampling the touch signals at sensor nodes adjacent to the maximum value and including the one or more neighboring signals in the extracted touch signal if an amplitude of the sampled signal is above a second threshold; and

sampling the touch signals at sensor nodes adjacent to the maximum value and including the one or more neighboring signals in the extracted touch signal until one of a number of sampled signals reach a third threshold, a value of the touch signal is below a fourth threshold, and a value of the touch signal is below a first threshold.

9. The method of claim 8 , further comprising discontinuing sampling when a difference between a value of one of the touch signals and values of neighboring touch signals is below a fifth threshold or when the number of signals in the extracted touch signal exceeds a predetermined threshold.

10. An apparatus for filtering a touch input, comprising:

a processor;

a touch device; and

a memory, operably coupled to the processor, and configured to store processor instructions that configure the processor to:

receive a touch input on a touch interface from a finger or a stylus, wherein receiving a touch input comprises receiving touch signals from a plurality of sensor nodes of the touch interface, the touch signals including information from each of the plurality of sensor nodes representing an x position value, a y position value, and an amplitude of the touch input;

determine an arithmetic mean of the touch input, the arithmetic mean indicating a first estimated touch position of the touch input on the touch surface;

determine a weighted mean of the touch input, wherein the weighted mean is determined in part by applying a higher weight to the touch signals having a higher amplitude, the weighted mean indicating a second estimated touch position of the touch input on the touch interface;

determine a difference between the weighted mean of the touch input and an arithmetic mean of the touch input; and

adjust the second estimated touch position of the touch input to a final estimated position based on the difference.

11. The apparatus of claim 10 , wherein the memory is further configured to store processor instructions that configure the processor to adjust one or more of the x position value, the y position value, and the amplitude of the second estimated touch position to the final estimated position based on the difference.

12. The apparatus of claim 11 , wherein adjusting the second estimated touch position to the final estimated touch position comprises adjusting the second estimated touch position to the value of the weighted mean when the difference is below a first threshold and to a value based on the difference when the difference is equal to or above the first threshold.

13. The apparatus of claim 10 , wherein the memory further is configured to store processor instructions that configure the processor to:

identify a maximum amplitude of the touch input of the plurality of touch signals.

14. The apparatus of claim 13 wherein the touch interface is divided into a plurality of sectors by sector divisions to determine which sectors of the touch interface contain shadow effects of the touch input.

15. The apparatus of claim 14 , wherein the sector divisions pass through one of a sensor node located closest to the weighted mean of the touch input or the arithmetic mean of the touch input.

16. The apparatus of claim 14 , wherein the touch interface is divided into sectors by sector divisions that pass through a sensor node of the touch interface having a maximum touch signal strength as compared to the touch signal strengths of all of the sensor nodes in the touch input.

17. The apparatus of claim 14 , wherein the memory further is configured to store processor instructions that configure the processor to:

sort the touch signals in a descending order list such that the touch signal with the highest value occurs first in the list;

determine a maximum value of the touch signals and adding the maximum value to an extracted touch signal;

sample the touch signals at sensor nodes adjacent to the maximum value and including the one or more neighboring signals in the extracted touch signal if an amplitude of the sampled signal is above a second threshold;

sample the touch signals at sensor nodes adjacent to the maximum value and including the one or more neighboring signals in the extracted touch signal until one of a number of sampled signals reach a third threshold, a value of the touch signal is below a fourth threshold, and a value of the touch signal is below a first threshold; and

discontinuing sampling when a difference between a value of one of the touch signals and values of neighboring touch signals is below a fifth threshold.

18. A system for filtering a touch input, comprising:

a control module configured to

receive a touch input on a touch interface from a finger or a stylus, wherein receiving a touch input comprises receiving touch signals from a plurality of sensor nodes of the touch interface, the touch signals including information from each of the plurality of sensor nodes representing an x position value, a y position value, and an amplitude of the touch input;

determine an arithmetic mean of the touch input, the arithmetic mean indicating a first estimated touch position of the touch input on the touch surface;

determine a weighted mean of the touch input, wherein the weighted mean is determined in part by applying a higher weight to the touch signals having a higher amplitude, the weighted mean indicating an estimated second touch position of the touch input on the touch interface;

determine a difference between the weighted mean of the touch input and an arithmetic mean of the touch input; and

adjust the second estimated touch position to a final estimated touch position of the touch input based on the difference.

19. The system of claim 18 , wherein the control module is configured to adjust one or more of the x position value, the y position value, and the amplitude of the second estimated touch position based on the difference between the weighted mean of the touch input and an arithmetic mean of the touch input, and wherein adjusting the second estimated touch position comprises adjusting the second estimated touch position to the value of the weighted mean when the difference is below a first threshold and to a value based on the difference when the difference is equal to or above the first threshold.

20. The system of claim 18 , wherein the control module is further configured to:

identify a maximum amplitude of the touch input of the plurality of touch signals.

21. The system of claim 20 wherein the touch interface is divided into a plurality of sectors by sector divisions to determine which sectors of the touch interface contain shadow effects of the touch input.

22. The system of claim 21 , wherein the sector divisions pass through one of a sensor node located closest the weighted mean of the touch input, the arithmetic mean of the touch input, or a sensor node of the touch interface having a maximum touch signal strength as compared to the touch signal strengths of all of the sensor nodes in the touch input.

23. The system of claim 20 , wherein the control module is further configured to:

sort the touch signals in a descending order list such that the touch signal with the highest value occurs first in the list;

determine a maximum value of the touch signals and adding the maximum value to an extracted touch signal;

sample the touch signals at sensor nodes adjacent to the maximum value and including the one or more neighboring signals in the extracted touch signal if an amplitude of the sampled signal is above a second threshold;

sample the touch signals at sensor nodes adjacent to the maximum value and including the one or more neighboring signals in the extracted touch signal until one of a number of sampled signals reach a third threshold, a value of the touch signal is below a fourth threshold, and a value of the touch signal is below a first threshold; and

discontinuing sampling when a difference between a value of one of the touch signals and values of neighboring touch signals is below a fifth threshold.

24. A non-transitory computer-readable medium storing instructions that, when executed, cause at least one physical computer processor to perform a method of reducing shadow effects in a touch system, the method comprising:

receiving a touch input on a touch interface from a finger or a stylus, wherein receiving a touch input comprises receiving touch signals from a plurality of sensor nodes of the touch interface, the touch signals including information from each of the plurality of sensor nodes representing an x position value, a y position value, and an amplitude of the touch input;

determining an arithmetic mean of the touch input, the arithmetic mean indicating a first estimated touch position of the touch input on the touch surface;

determining a weighted mean of the touch input, wherein the weighted mean is determined in part by applying a higher weight to the touch signals having a higher amplitude, the weighted mean indicating a second estimated touch position of the touch input on the touch interface;

determining a difference between the weighted mean of the touch input and the arithmetic mean of the touch input; and

adjusting the second estimated touch position of the touch input to a final estimated touch position based on the difference.

25. The non-transitory computer-readable medium of claim 24 , wherein adjusting the second estimated position of the touch input comprises adjusting one or more of the x position value, the y position value, and the amplitude of the second estimated touch position based on the difference between the weighted mean of the touch input and the arithmetic mean of the touch input, and adjusting the second estimated touch position comprises adjusting the second estimated touch position to the value of the weighted mean when the difference is below a first threshold and to a value based on the difference when the difference is equal to or above the first threshold.

26. The non-transitory computer-readable medium of claim 24 , further comprising

identifying a maximum amplitude of the touch input of the plurality of touch signals.

27. The non-transitory computer-readable medium of claim 26 , wherein the touch interface is divided into a plurality of sectors by sector divisions to determine which sectors of the touch interface contain shadow effects of the touch input and wherein the sector divisions pass through one of a sensor node located closest to the weighted mean of the touch input, the arithmetic mean of the touch input, or a sensor node of the touch interface having a maximum touch signal strength as compared to the touch signal strengths of all of the sensor nodes in the touch input.

28. The non-transitory computer-readable medium of claim 26 , further comprising:

sorting the touch signals in a descending order list such that the touch signal with the highest value occurs first in the list;

determining a maximum value of the touch signals and adding the maximum value to an extracted touch signal;

sampling the touch signals at sensor nodes adjacent to the maximum value and including the one or more neighboring signals in the extracted touch signal if an amplitude of the sampled signal is above a second threshold;

sampling the touch signals at sensor nodes adjacent to the maximum value and including the one or more neighboring signals in the extracted touch signal until one of a number of sampled signals reach a third threshold, a value of the touch signal is below a fourth threshold, and a value of the touch signal is below a first threshold; and

discontinuing sampling when a difference between a value of one of the plurality of touch signals and values of neighboring touch signals is below a fifth threshold.